I'm having some trouble implementing a SPI communication between the ESP32 (SLAVE) and the nrf51-dk (MASTER).
Basically, what I'm trying to do is sending a char array from the nrf51 to the ESP32. In order to do so, I'm running a Mbed SPI Master example and trying to receive the array with the esp-idf example (peripherals/spi_slave/receiver). Unfortunately, after the transmission is done, no valid information is received. I also notice that, in most of the cases, my RX buffer is empty or with just a random value on the first element of the array. I've tried connecting the MISO pin on the MOSI pin on each board, and, in both cases, the boards got able to send and receive their own transmissions.
The NRF51 mbed Code:
Code: nrf51.cpp Select all
#include <mbed.h>
Serial pc(USBTX, USBRX); //UART
SPI spi(SPI_PSELMOSI0,SPI_PSELMISO0,SPI_PSELSCK0);//SPI
DigitalIn handshake(p23); //SPI Handshake Pin
DigitalOut cs(SPI_PSELSS0); //SPI Chip Select
int main() {
cs = 1; //Disable Slave
pc.baud(9600); //UART Init
pc.printf("Starting...\n\r");
spi.format(8,3); //SPI 8 bits, Mode 3
spi.frequency(1000000); // 1 MHz clock
while(1) {
//RX TX Buffers
char tx_buffer[128] = {"MASTER TX BUFFER"};
char tx_length = 128;
char rx_buffer[128] = {"MASTER RX BUFFER"};
char rx_length = 128;
cs = 0; //Enable Slave
while(!handshake){} // Wait for slave to be available
spi.write(tx_buffer, tx_length, rx_buffer, rx_length); //Transmission
cs = 1; // Disable Slave
pc.printf("String:\n\r"); //Print RX Buffer
for(i = 0; i < 128 ; i++){
pc.printf("%c", rx_buffer[i]);
}
pc.printf("\n\r");
wait(5); // Wait
}
}
On the ESP32 I'm running the SPI_Slave (Receiver) example with a few changes:
- SPI mode 3
- Added the Attribute WORD_ALIGNED_ATTR to recvbuf and sendbuf
- Changed the transmission String
Code: esp32.cpp Select all
#include <stdio.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/semphr.h"
#include "freertos/queue.h"
#include "lwip/sockets.h"
#include "lwip/dns.h"
#include "lwip/netdb.h"
#include "lwip/igmp.h"
#include "esp_wifi.h"
#include "esp_system.h"
#include "esp_event.h"
#include "esp_event_loop.h"
#include "nvs_flash.h"
#include "soc/rtc_cntl_reg.h"
#include "esp32/rom/cache.h"
#include "driver/spi_slave.h"
#include "esp_log.h"
#include "esp_spi_flash.h"
#define GPIO_HANDSHAKE 2
#define GPIO_MOSI 12
#define GPIO_MISO 13
#define GPIO_SCLK 15
#define GPIO_CS 14
void my_post_setup_cb(spi_slave_transaction_t *trans) {
WRITE_PERI_REG(GPIO_OUT_W1TS_REG, (1<<GPIO_HANDSHAKE));
}
void my_post_trans_cb(spi_slave_transaction_t *trans) {
WRITE_PERI_REG(GPIO_OUT_W1TC_REG, (1<<GPIO_HANDSHAKE));
}
void app_main()
{
int n=0;
esp_err_t ret;
spi_bus_config_t buscfg={
.mosi_io_num=GPIO_MOSI,
.miso_io_num=GPIO_MISO,
.sclk_io_num=GPIO_SCLK
};
spi_slave_interface_config_t slvcfg={
.mode=3, // Changed to mode 3
.spics_io_num=GPIO_CS,
.queue_size=3,
.flags=0,
.post_setup_cb=my_post_setup_cb,
.post_trans_cb=my_post_trans_cb
};
gpio_config_t io_conf={
.intr_type=GPIO_INTR_DISABLE,
.mode=GPIO_MODE_OUTPUT,
.pin_bit_mask=(1<<GPIO_HANDSHAKE)
};
gpio_config(&io_conf);
gpio_set_pull_mode(GPIO_MOSI, GPIO_PULLUP_ONLY);
gpio_set_pull_mode(GPIO_SCLK, GPIO_PULLUP_ONLY);
gpio_set_pull_mode(GPIO_CS, GPIO_PULLUP_ONLY);
ret=spi_slave_initialize(HSPI_HOST, &buscfg, &slvcfg, 1);
assert(ret==ESP_OK);
WORD_ALIGNED_ATTR char sendbuf[129]=""; // Added the WORD ALIGNED Attribute
WORD_ALIGNED_ATTR char recvbuf[129]="";
memset(recvbuf, 0, 33);
spi_slave_transaction_t t;
memset(&t, 0, sizeof(t));
while(1) {
memset(recvbuf, 0xA5, 129);
sprintf(sendbuf, "SLAVE TX BUFFER"); // Changed String
t.length=128*8;
t.tx_buffer=sendbuf;
t.rx_buffer=recvbuf;
ret=spi_slave_transmit(HSPI_HOST, &t, portMAX_DELAY);
printf("Received: %s\n", recvbuf);
n++;
}
}